Production of solid carbon dioxide



J. R. CHAMBERLAIN PRODUCTION OF SOLID CARBON DIOXIDE Filed March 14 1932 dttorncgs Patented Dec. 11, 1934 UNITED STATES PATENT OFFICE 8 Olaima'. (01. 62121) This invention relates to refrigeration, and particularly to methods and apparatus for the production of solid carbon dioxide.

The most important aspect of the invention is the idea of supplying to the solidifying expanders (snow machines, for example), liquid carbon dioxide at a substantially uniform low temperature, preferably as low a temperature as can be usedunder commercial conditions without danger of freeze-ups.

Important contributing factors are the use, as the reservoir for such liquid, of an intermediate receiver having an interstage connection with a stage compressing system. Uniform temperature in the intermediate receiver is dependent on uniform pressure therein. While such uniformity of receiver pressure can be established by proper relation of the stages of compression, using a free connection between the receiver and interstage connection, it is considered simpler and commercially more satisfactory to permit the interstage pressure to vary in a range always below the desired intermediate receiver pressure, and to interpose between the receiver and the interstage connection a'valve which maintains receiver pressure substantially constant, by controlling flow from the receiver to the interstage connection.

Other important features are the use of a high side float to ensure a liquid seal between the the condenser and the intermediate receiver, or the use of equivalent means to the end that only liquid enters the receiver; the use of cooling means which ensures that the condenser for carbon dioxide always operates below the critical temperature; and the use of a sight glass to indicate to the snow machine operator that an adequate quantity of liquid is present in the intermediate receiver.

The invention will now be described with reference to the accompanying drawing, in which,-

Fig. 1 is a diagrammatic elevation of the complete system.

Fig. 21s an enlarged section of the high side float valve which admits liquid refrigerant from the condenser to the intermediate receiver.

Fig. 3 is an enlarged section of the relief valve which maintains a substantially constant pressure in the intermediate receiver by regulating flow to an interstage connection.

In the drawing, a carbon dioxide gas supply pipe is indicated at*10, the same being connected to the intake of compressor 11, in which the gas is compressed to approximately ninety pounds per square inch. From compressor 11, the gas passes through intercooler 12 to a second compressor 13, in which the pressure is brought up to approximately 450 pounds per square inch,

and then passed through after-cooler 14 to condenser '15. cooled. Condenser 15 consists of a plurality of shells 16 in series and longitudinal tubes 17 therein connected to surge drum 18 disposed above the condenser. Condensation of the carbon dioxide is effected by heat exchange between 'the gas and liquid ammonia, the temperature of which is lowered by evaporation thereof in the tubes 17.

The ammonia circuit comprises a compressor 19, condenser 21, high side float valve 22, and suction and pressure lines 23, 24, respectively.

From condenser 15 liquefied CO: is discharged through high side float valve 25 into intermediate receiver 26. A combined check valve and relief valve 2'7 is interposed between receiver 26 and pipe 28 connecting the receiver with the interstage connection between compressors 11 and 13, preventing the pressure in the receiver from exceeding a predetermined amount, and acting as a check valve when the receiver pressure falls below that in the connection between the low and high stage compressors. Normally, the relief valve is set to maintain a predetermined pressure in the receiver, corresponding with the temperature at which it is. desired to maintain the liquid therein, the liquid CO: evaporating in part until the temperature corresponding to the maintained pressure is reached, and the resulting gas escaping through the relief valve and pipe 28 to the second stage compressor While the form of the elements 22, 25 and 27, is subject to variation, satisfactory commercial valves are illustrated in Figs. 2 and 3.

In Fig. 2 the construction of the high side float valves 22 and 25 is clearly shown. The float chamber 41 is supplied with liquid refrigerant through connection 42. The float 43 ri'sing with the rise of liquid level moves valve 44 in an opening direction. Valve 44 controls a discharge connection 45.

In Fig. 3 the construction of the valve 27 is illustrated. Between the body 27 and cap 46' a flexible diaphragm 47 is clamped. This is subject on its lower side to pressure in receiver 26, arriving by way of connection 48. A loading spring. 49 with adjusting thrust screw 51. op-

' poses receiver pressure. A- partition52 in body Coolers 12 and 14 are both water Y 27 carries the slotted sleeve 53 which is closed -snow chambers.

at its upper end and serves as a seat for the slotted valve sleeve 54 which encircles it. Sleeve 54 is thus a balanced valve opening when diaphragm 47 yields upward. A light spring 55 urges valve sleeve 54 into thrust engagement with diaphragm 47. The valve opens only when receiver pressure'exceeds a-chosen value and is not affected by interstage pressure admitted through interstage connection 28.

It is possible, of course, so to design the compressors that a constant pressure is maintained in the connection between. the compressors. This pressure may correspond with the receiver pressure at which the liquid in the receiver is reduced to the desired temperature prior to expansion of the liquid, in which case the expanding carbon dioxide may be by-passed around the relief valve.

By reducing the pressure in receiver 26, the liquid CO2 which enters float valve chamber 25 at a temperature of about 17 F. is cooled to the temperature corresponding to the pressure in the receiver, i. e., approximately 50 F. The sub-cooled liquid carbon dioxide is now conducted through pipe 29 and branches 31, 31 to expansion chambers 32, 32, wherein it expands to convert a portion thereof to a solid snowlike form of carbon dioxide. Valves 33, 33' control the volume of liquid discharged into the expansion chambers. A definite volume of liquid at a definite temperature will produce a definite weight of solid carbon dioxide and flash gas, so that simple control of the volume of liquid discharged to the expansion chamber for each batch determines the weight of solid carbon dioxide in each batch. The gas evolved in the expansion chamber is then returned through pipe 34 to the inlet side of the first stage compressor 11.

In order to prevent interference with the operation of the apparatus from freezing of water which may find its way into the system, it is proposed to install duplicate receivers 26 with suitable connections to shut down one for repairs and permit discharge from the other to the Suitable valved by-passes are also provided for float valve 25 and relief valve 27, as indicated at 35 and 36, respectively. The by-pass valves are normally closed.

v It is important that, when valves 33, 33' are open, liquid C02 be available in sufficient quantity in receiver 26 for expansion in chambers 32, 32'. While float valve 25 provides for regulated discharge of condensate to the receiver, there is provided on the receiver a liquid level gage 3'7 to enable the operator visually to deterties,, discharges liquid to the snow chamber in regulated quantities, and provides for emcient abstraction of sensible heat from the carbon dioxide by cooling in heat exchange with ammonia, followed by partial expansion prior to delivery of the CO: tothe snow chamber. The ammonia circuit, or primary cooling unit, is

I dependent only on water at ordinary temperatures forcondensing. It is, therefore, apparent that the apparatus will function efficiently regardless of atmospheric conditions.

While the use of a secondary refrigerating circuit to cool the carbon dioxide condenser is preferred, it is typical of any means to ensure cooling below and preferably substantially below the critical temperature for carbon dioxide at all times. Consequently liquid carbon dioxide is fed continuously to high side float valve 25, and the valve is liquid sealed to preclude the entrance of gaseous refrigerant into receiver 26. The valve 27 functions to maintain a substantially constant pressure, and hence a substantially constant temperature in receiver 26;

The maintenance of constant liquid tempera ture and the gage 37, make it possible for the operator to control his snow machine intelligently; For example, where these snow machines press each batch of snow into a block intended to weigh 50 pounds, the maximum variation in weight can be held within 2 pounds merely by timing the period valve 33 (or 33) remains open. In. one commercial installation such period was 15 seconds.

The installation herein described is intended to be illustrative rather than limiting, contemplated limitationsbeing expressed in the claims.

What is claimed is:-

1. A system for solidifying carbon dioxide, comprising in combination, compressing means; a condenser fed thereby; a receiver; means interposed between the condenser and the receiver for protecting the receiver from the pressure existing in the condenser and for assuring the admission. of liquefied carbon dioxide alone from the condenser to the receiver; means for maintaining said receiver at a substantially uniform pressure intermediate between condenser pressure and the suction pressure of said compressing means; a solidifying expander interposed in a connection between the liquid space in said receiver and the suction of said compressing means; and means for supplying carbon dioxide to the system.

2. A system for solidifying carbon dioxide, comprising in combination, means for compressing carbon dioxide in stages; a condenser for cooling such carbon dioxide; a receiver; means for feeding carbon dioxide from the condenser to the receiver while protecting said receiver against condenser pressure; a vaporconnection from said receiver to a'point in the system between compressing stages; means in the lastnamed connection responsive at least in part to pressure in said receiver and serving to maintain receiver pressure at a substantially uniform value intermediate between condenser pressure and the suction. pressure of said compressing means; a snow machine interposed between the liquid space in said receiver and the suction of said compressing means; and means for supplying carbon dioxide to the system.

3. The combination of stage compressing means having an interstage connection; a condenser fed by said compressing means; a high side float valve fed by said condenser; a receiver fed by said float valve; a pressure maintaining valve interposed in a connection between the vapor space in said receiver and said interstage connection and serving to maintain in said receiver a substantially uniform pressure intermediate between condenser pressure and the suc tion pressure of said compressing means; a solidifying expander having a liquid supply connection fed by said receiver, and a flash gas connection leading from the expander to the suction ofv said compressing means; and means for supplying carbon dioxide to the system. v 1

4. The combination defined in claim 3, in which the condenser is maintained at a temperature substantially below the critical temperature of carbon dioxide by means of a reversed heat cycle performed with a refrigerant having a ing pressure; then liquei'y'ing it; then cooling th liquid carbon dioxide to a definite low temperature by permitting a portion of it to boil of! to a uniform pressure and delivering the result-' ing vapor to a point in said circuit at a relatively low pressure; and feeding the liquid carbon dioxide so cooled through an expansion chamber to the point of lowest pressure in the circuit; and withdrawing snow from the expansion 6. The method of producing carbon dioxide snow, which comprises supplying carbon dioxide to a circuit inwhich thecarbon dioxide may circulate repeatedly and from which the formed carbon dioxide snow is withdrawn; and in said circuit subjecting the carbon dioxide to increasing pressure: then liquefying it; then cooling the liquid carbon dioxide to a definite low temperature bypermitting a portion of it to boil oil to a uniform premure and delivering the resulting vapor to a point in said circuit at a relatively low pressure; and intermittently feeding the in the circuit; and withdrawing snow from the a expansion chamber.

JOSEPH R. GHAMBERLAIN.

mber. 

